Hi all

Hoping for some help on a problem with the Engine Warning light coming on Fiesta that my daughter has recently taken ownership of.

Warning light came on after she'd driven an initial 200+ miles (on motorway journey), got reset by RAC (there diagnostic screen read-out attached), but then came on again after another 100 miles or so. We took it to a highly recommended/trustworthy garage who reset light & ran diagnostics/tests but couldn't replicate problem (including after 80 mile test drive). I've attached there diagnostic print-out to which appears to show all fine. They suggested/recommended could be poor fuel (shed filled it twice since owning at Supermarket) and recommended using premium fuels only for a bit to see if OK. Prior to returning car to her (she lives 160 miles away) I took it for a 90 mile run this morning and then filled tank to brim with Shell V-power (it was down to last 100 miles on tank). All fine until 5 miles later turning onto my driveway the warning light came back on 😟.

The garage completing the test said they believe (based on readings) CAT is all fine & sensors not faulty as all performed as they should do with test.

Not sure where to go next with it - can appreciate chasing 'ghost diagnostics' can take an age and cost a fortune. 

Trying to get problem sorted before returning car to her as she lives 160 miles away & needs a reliable/consistent car with a 70 mile daily commute with shift work start/end times

I've seen suggestions of fuel cap seal leak being a possible issue (??) but any tips/recommendations appreciated.

 

Cheers

Nick

Car just on the three  year point, Ford might look at it for you if the car has stayed in the dealer network.

If the engine warning light has come on there will be a fault code stored. You need to find out what this is to diagnose further. 
 

Also you said she’d recently taken ownership. How long ago and was it from a business or private seller?

27 minutes ago, anon said:

Car just on the three  year point, Ford might look at it for you if the car has stayed in the dealer network.

Thanks - Not sure on exact date, but I think its over 3.5 years since actual Registration so I suspect they wont be too keen?

9 minutes ago, alexp999 said:

If the engine warning light has come on there will be a fault code stored. You need to find out what this is to diagnose further. 
 

Also you said she’d recently taken ownership. How long ago and was it from a business or private seller?

Thanks for reply.  We've got the original fault code (and suspect it's the same now) shown in the RAC log as P0420?

 

It was effectively a private purchase through a 'friend of a friend' but not someone we have a direct contact with. Not a lot of scope to go back to them as we would with a trade supply I think. Suspicion would be they might of known of the problem, but difficult to prove and even then probably cant take it anywhere.

Depends. If the mileage is not too high, they might do it cheaply as a goodwill gesture. They would like to sell you a new one and make a profit on your old one, too so a bit of good service won't go amiss with a bit of buttering them up.

Ah, no probability of any joy with Ford, then so time for a good diagnostician to analyse what could be causing the fault code. The code is for the catlytic converter which is operating inefficiently. It has a sensor at the back end which monitors the oxygen level of what comes out. What goes in is managed by another sensor at the front end. This sensor adjusts the engine's settings for the required efficiency and the one at the back checks that it has done so. If either of them gets upset, the light comes on and the fault code is stored. The clever bit is to work out if anything is actually wrong or if the front end sensor has gone a bit off and is sending the wrong signals to the big black box  which doesn't know any better than it's told. It is more often the former. The back one is usually more reliable because it runs cooler.  This is well known so it is quite possible that  the previous owner fitted a new one and it didn't work because he chose the wrong one. It is also possible that this fault might clear itself by filling it with good fuel and then running it up a motorway for a couple of hundred miles to get the whole engine warmed through.  You need to take this knowledge to a trustworthy garage and ask them to read the outputs of both sensors. 

7 minutes ago, NIckBS said:

Thanks for reply.  We've got the original fault code (and suspect it's the same now) shown in the RAC log as P0420?

 

It was effectively a private purchase through a 'friend of a friend' but not someone we have a direct contact with. Not a lot of scope to go back to them as we would with a trade supply I think. Suspicion would be they might of known of the problem, but difficult to prove and even then probably cant take it anywhere.

Ah I see now. Picture didn’t load for me first time. If it’s private seller then you’ve got no come back I was only asking in the chance it might have been a business seller. 
 

If the cat is working fine then it could well be a sensor. Perhaps intermittent fault or a connection issue. 

1 hour ago, NIckBS said:

needs a reliable/consistent car with a 70 mile daily commute

Not that this helps fix the issue you have, but why would you choose a petrol 1.0 ecoboost to do those sort of miles each day ? and thats not even thinking about the 160 mile distance between each other. I would be thinking of trading it in and getting a 1.5 diesel.

Why? The car is both reliable and economical. You have a dislike of the Ecoboost and often express it but the fact remains that millions of the engine have been built and the vast majority of them are still giving good service. Your prejudice against the engine is in danger of spilling out into giving less good advice than that of which you are capable.

36 minutes ago, unofix said:

Not that this helps fix the issue you have, but why would you choose a petrol 1.0 ecoboost to do those sort of miles each day ? and thats not even thinking about the 160 mile distance between each other. I would be thinking of trading it in and getting a 1.5 diesel.

Because she lives in Central Birmingham and due to clean air zone charges she'd be liable for an £8/day charge for most diesel options.....

2 minutes ago, NIckBS said:

due to clean air zone charges she'd be liable for an £8/day charge

Ah! that makes sence. She needs to get a 1.0V Tesla 😉

3 hours ago, unofix said:

Ah! that makes sence. She needs to get a 1.0V Tesla 😉

I think the budget for that may be a few years down the line. She’s stretched further than intended to get this car due to challenges sourcing a decent 2nd hand car in the current market! 

5 hours ago, NIckBS said:

I took it for a 90 mile run this morning and then filled tank to brim with Shell V-power (it was down to last 100 miles on tank). All fine until 5 miles later turning onto my driveway the warning light came back on 😟.

Just for info, some of the monitoring that cars do including Catalyst monitoring amongst other things is only done when there is a certain level of fuel in the tank, typically 15% so that may be the reason that the fault was flagged up in the conditions you describe above. Other boxes need to be ticked during the drive cycle as well for the monitoring to be successfully completed.

I'm not saying that it is definitely the Cat that is near the end of its life and that does not explain why it did not happen when the Garage had it on a long test drive.

The other thing I would say is that if either of the O2 sensors were playing up then I would expect a fault code to be logged for them as well. I'm not trying to suggest that they must be perfectly ok, one or both may be near the end of their life.    

You only know if the sensor is playing up from the other fault codes around it. The trouble is that the code records symptoms and not necessarily the causes of the symptoms. Take a simple torch. The light will not come on.  Sensor logs a fault saying no current is flowing but it then takes diagnostic skills by people to work out if the battery, bulb or switch is at fault.

Thankfully Ford has not left any space for guessing , attached are two files , a DTC chart where you would search for your trouble code, which in this case would be P0420, you would find possible causes for that code, and it will redirect you to a relative " PinPoint test" which yo will find in the other file for a thorough diagnosis step by step with a yes and no procedure.

These are official Ford service manual files, hope this helps 🙂 

DTC Chart.pdf PinPoint tests.pdf

I'm sure they will help me a lot and in turn I shall be able to help others -Salaam, Ahmad.

Thanks for all the additional feedback & suggestions. Much appreciated.

 

We’re in the process of getting a 2nd opinion on the diagnostics from another garage.  The suggestion seems to be heading towards a faulty CAT as all sensors otherwise appear to be testing fine. A bit more caution being exercised before they change that, but seems most likely option as things stand.

24 minutes ago, NIckBS said:

We’re in the process of getting a 2nd opinion on the diagnostics from another garage.  The suggestion seems to be heading towards a faulty CAT as all sensors otherwise appear to be testing fine. A bit more caution being exercised before they change that, but seems most likely option as things stand.

Without having the car in front of me, that was my thought too even if my answer might not have spelled it out unless you can read between the lines. I didn't want you to get a new Cat that would not have solved the problem, and still don't, until other causes have been eliminated. 

The front Wideband O2 Sensors that you will have do not behave like the older narrowband ones and that does make old style diagnostics more difficult and a lot of cheap Code Readers can't even get Live Data from them. Ford do have a comprehensive list of fault codes that I would have expected to have been triggered if they were faulty. Both the O2 Sensors are monitored too and will throw up a code once they pass a certain threshold as well as if they are completely faulty. Worst case scenario would be if the rear one was a bit slow but not enough to trigger a fault and the Cat was near the end of its life too.

I would expect the garage to check the Misfire monitors and signs that the engine was burning oil because these would need fixed otherwise they will destroy a new Cat if one is fitted.

The annoying thing for you is that according to the screenshot the fault was logged 25 times before your daughter got the car, so the seller must have known.

Good luck and I hope it does not cost too much whatever the outcome. 

The success of the diagnostics will depend on who does it.  

 

1 hour ago, Eng_Ahmad1986 said:

Thankfully Ford has not left any space for guessing , attached are two files , a DTC chart where you would search for your trouble code, which in this case would be P0420, you would find possible causes for that code, and it will redirect you to a relative " PinPoint test" which yo will find in the other file for a thorough diagnosis step by step with a yes and no procedure.

These are official Ford service manual files, hope this helps 🙂 

DTC Chart.pdf 1.33 MB · 4 downloads PinPoint tests.pdf 3.73 MB · 3 downloads

Thanks Ahmad, I don't know how you get this stuff but it is very valuable.

1 hour ago, Tizer said:

Without having the car in front of me, that was my thought too even if my answer might not have spelled it out unless you can read between the lines. I didn't want you to get a new Cat that would not have solved the problem, and still don't, until other causes have been eliminated. 

The front Wideband O2 Sensors that you will have do not behave like the older narrowband ones and that does make old style diagnostics more difficult and a lot of cheap Code Readers can't even get Live Data from them. Ford do have a comprehensive list of fault codes that I would have expected to have been triggered if they were faulty. Both the O2 Sensors are monitored too and will throw up a code once they pass a certain threshold as well as if they are completely faulty. Worst case scenario would be if the rear one was a bit slow but not enough to trigger a fault and the Cat was near the end of its life too.

I would expect the garage to check the Misfire monitors and signs that the engine was burning oil because these would need fixed otherwise they will destroy a new Cat if one is fitted.

The annoying thing for you is that according to the screenshot the fault was logged 25 times before your daughter got the car, so the seller must have known.

Good luck and I hope it does not cost too much whatever the outcome. 

The success of the diagnostics will depend on who does it.  

 

Thanks for that insight - all very useful. Hadn’t spotted / understood the indication of the fault being logged 25 times. Will get garage to confirm they’ve looked at misfires/ burning oil as you suggest. 
 

Cheers, Nick